Capricorn 16. An invisible skull reveals a living human brain, its surface flickering with rainbows.
A certain Alchemist of Taruz had to power to make both his face and his skull invisible. He used this ability to frequently test the progress of his students, for when he allowed them to see in his brain they witnessed there the everchanging colors of his thoughts as they moved across his brain like the Aurora Borealis in the night sky, which are the thoughts of God.
After a time of observing he then asked them to tell him what they saw. He found that the more advanced of his disciples were able to translate the colors they observed into words that more or less accurately described what he had been thinking. The most advanced ones had the power to translate his inner colors spontaneously into the most beautiful and mysterious poetry.